The present invention relates to switching units for use in circuit-switched networks and particularly to the processing of incoming and outgoing call requests of varying priorities at a switching unit.
In the majority of business establishments connected to a public or private switched telephone network, the number of potential users of data and telephony services is usually greater than the number of available external interfaces to the network. To manage the allocation of bandwidth on the external interfaces (e.g., external telephone lines) to internal users, businesses usually rely on the use of a switching unit such as a private branch exchange (PBX) or a key system unit (KSU).
The heart of a PBX or KSU is a switch matrix for establishing one-to-one connections between a plurality of bandwidth channels on a number of external lines and, usually, an even greater plurality of bandwidth channels on a number of internal lines. In some cases, internal lines are directly connected to individual terminal devices such as digital telephones, personal computers and point-of-sale terminal adapters (e.g., credit card readers). In other cases, an internal line may be connected to a more sophisticated piece of equipment, such as an Ethernet router/hub or a dialup network terminal adapter, which may be capable of carrying a plurality of bandwidth channels to several of the just mentioned terminal devices.
Generally, the type of connection established between a terminal device and the external network through the switching unit is classifiable as being either a voice or a data connection. A voice connection is usually bidirectional and typically requires the establishment and continuous occupancy of a single circuit joining a bandwidth channel on an external line to a bandwidth channel on the internal line corresponding to the terminal device placing or receiving the call.
On the other hand, a data connection often consists of spurious, unidirectional exchanges of packets which occasionally requires the establishment of additional circuits or the removal of unused ones. Although there is a clear dichotomy between the constant bandwidth requirements of voice and the variable bandwidth requirements of packet-based data communications, both types of information must share the same amount of external network bandwidth available to the switching unit.
Moreover, it is recognized that real-time exchanges such as telephone conversations will generally have a higher priority than store-and-forward data transactions, e.g., E-mail messages. Thus, the nature and priority of a call (or call request) must be taken into account by any system which is to allow voice and data circuits to efficiently and equitably share the same xe2x80x9cpoolxe2x80x9d of bandwidth channels carried by the external lines.
Currently, the most common form of bandwidth management uses line pool servers for allocating a fixed number of external bandwidth channels to voice and a fixed number of external bandwidth channels to data. While this allows a certain minimum number of connections (i.e., circuits) to be established for either type of information exchange, there will always exist conditions under which the fixed allocation will prove inefficient, either because unused data bandwidth channels are not being used for voice or because unused voice bandwidth channels are not being employed for data.
Furthermore, even when the available bandwidth channels carried by the external lines are allocated in a dynamic fashion by the line pool server, switching units employing this technique remain at a disadvantage when faced with a shortage of available bandwidth channels, since the line pool server is not designed to take into account the relative priorities of existing calls and newly made call requests. Clearly, such switching units suffer from being unable to tear down lower-priority connections in order to establish higher-priority connections in their stead.
It is an object of the present invention to mitigate or obviate one or more disadvantages of the prior art.
Therefore, the invention may be summarized according to a first broad aspect as a switching unit connectable to a plurality of external lines carrying a plurality of external bandwidth channels and also connectable to a plurality of internal lines carrying a plurality of internal bandwidth channels, the switch comprising: a plurality of internal interface units connectable to the internal lines, for receiving outgoing call requests associated with respective internal bandwidth channels; a control unit connected to the internal interface units, for receiving outgoing call requests from the internal interface units and generating respective updated circuit mappings therefrom; and a switch connected to the control unit and to the internal interface units and connectable to the external lines, for controllably establishing circuits between the external bandwidth channels and respective ones of the internal bandwidth channels in accordance with updated circuit mappings received from the control unit; wherein the control unit comprises means for, upon receiving an outgoing call request, determining whether there is an available external bandwidth channel and if so: generating an updated circuit mapping sent to the switch for establishing a circuit between the available external bandwidth channel and the internal bandwidth channel associated with said outgoing call request; otherwise: determining whether the outgoing call request has a higher priority than at least one currently established circuit and if so, generating an updated circuit mapping sent to the switch for interrupting a lower-priority circuit and establishing a new circuit between the external bandwidth channel formerly associated with the interrupted circuit and the internal bandwidth channel associated with said outgoing call request.
In a switching unit comprising a switch for controllably establishing circuits between a plurality of external bandwidth channels and respective ones of a plurality of internal bandwidth channels, the invention may be summarized according to a second broad aspect as a method of processing an outgoing call request associated with an internal bandwidth channel, said outgoing call request having a priority, the method comprising the steps of: determining whether there is an available external bandwidth channel and if so: establishing a circuit between the available external bandwidth channel and the internal bandwidth channel associated with said outgoing call request; otherwise: determining whether the outgoing call request has a higher priority than at least one currently established circuit and if so, interrupting a lower-priority circuit and establishing a new circuit between the external bandwidth channel formerly associated with the interrupted circuit and the internal bandwidth channel associated with said outgoing call request..
The invention may be summarized according to a third broad aspect as a computer-readable storage medium containing software which, when running on a processor in a switching unit for controllably establishing circuits between a plurality of external bandwidth channels and respective ones of a plurality of internal bandwidth channels, follows a sequence of steps to process an outgoing call request associate with an internal bandwidth channel and having a priority, the steps comprising: determining whether there is an available external bandwidth channel and if so: establishing a circuit between the available external bandwidth channel and the internal bandwidth channel associated with said outgoing call request; otherwise: determining whether the outgoing call request has a higher priority than at least one currently established circuit and if so, interrupting a lower-priority circuit and establishing a new circuit between the external bandwidth channel formerly associated with the interrupted circuit and the internal bandwidth channel associated with said outgoing call request.
According to a further broad aspect, the invention may be summarized as a switching unit connectable to at least one external line carrying a plurality external bandwidth channels and also connectable to at least one internal line carrying a plurality of internal bandwidth channels, the internal lines connected to terminal devices, the terminal devices associated with at least one of the plurality of internal bandwidth channels, the switch comprising: a plurality of external interface units connectable to the external lines, for receiving incoming call requests associated with the external bandwidth channels carried by the external lines; a control unit connected to the external interface units, for receiving incoming call requests from the external interface units and generating respective updated circuit mappings therefrom; and a switch connected to the control unit and to the external interface units and connectable to the internal lines, for controllably establishing circuits between the external bandwidth channels and respective ones of the internal bandwidth channels in accordance with updated circuit mappings received from the control unit; wherein the control unit comprises means for, upon receiving an incoming call request from an external interface unit, determining the destination terminal device and determining whether there is at least one available internal bandwidth channel associated with the destination terminal device and if so: if the external bandwidth channel carrying said incoming call request is available, generating an updated circuit mapping sent to the switch for establishing a circuit between an available internal bandwidth channel and the external bandwidth channel associated with said incoming call request; otherwise: determining whether the incoming call request has a higher priority than at least one circuit currently established with the destination terminal device and if so and also if the external bandwidth channel carrying said incoming call request is available, generating an updated circuit mapping sent to the switch for interrupting a lower-priority circuit occupying an internal bandwidth channel associated with the destination terminal device and establishing a new circuit between the internal bandwidth channel formerly associated with the interrupted circuit and the external bandwidth channel associated with said incoming call request.
In a switching unit comprising a switch for controllably establishing circuits between a plurality of external bandwidth channels and respective ones of a plurality of internal bandwidth channels, the invention may be summarized according to yet another broad aspect as a method of processing an incoming call request associated with an the external bandwidth channels, said incoming call request having a priority and associated with a destination terminal device and at least one internal bandwidth channel, the method comprising the steps of: determining whether there is at least one available internal bandwidth channel associated with the destination terminal device and if so: determining whether the external bandwidth channel carrying said incoming call request is available and if so, generating an updated circuit mapping sent to the switch for establishing a circuit between an available internal bandwidth channel and the external bandwidth channel associated with said incoming call request; otherwise: determining whether the incoming call request has a higher priority than at least one circuit currently established with the destination terminal device and if so, determining whether the external bandwidth channel carrying said incoming call request is available and if so, generating an updated circuit mapping sent to the switch for interrupting a lower-priority circuit occupying an internal bandwidth channel associated with the destination terminal device and establishing a new circuit between the internal bandwidth channel formerly associated with the interrupted circuit and the external bandwidth channel associated with said incoming call request.
The invention may be summarized according to still another broad aspect as a computer-readable storage medium containing software which, when running on a processor in a switching unit for controllably establishing circuits between a plurality of external bandwidth channels and respective ones of a plurality of internal bandwidth channels, follows a sequence of steps to process an incoming call request having a priority, the steps comprising: determining whether there is at least one available internal bandwidth channel associated with the destination terminal device and if so: determining whether the external bandwidth channel carrying said incoming call request is available and if so, generating an updated circuit mapping sent to the switch for establishing a circuit between an available internal bandwidth channel and the external bandwidth channel on which said incoming call request was received; otherwise: determining whether the incoming call request has a higher priority than at least one circuit currently established with the destination terminal device and if so, determining whether the external bandwidth channel carrying said incoming call request is available and if so, generating an updated circuit mapping sent to the switch for interrupting a lower-priority circuit occupying an internal bandwidth channel associated with the destination terminal device and establishing a new circuit between the internal bandwidth channel formerly associated with the interrupted circuit and the external bandwidth channel carrying said incoming call request.